"доброу" meaning in Vieux slave

{
  "categories": [
    {
      "kind": "other",
      "name": "Formes d’adjectifs en vieux slave",
      "parents": [],
      "source": "w"
    },
    {
      "kind": "other",
      "name": "Vieux slave",
      "orig": "vieux slave",
      "parents": [],
      "source": "w"
    }
  ],
  "lang": "Vieux slave",
  "lang_code": "cu",
  "pos": "adj",
  "pos_title": "Forme d’adjectif",
  "senses": [
    {
      "form_of": [
        {
          "word": "добръ"
        }
      ],
      "glosses": [
        "Datif singulier de добръ."
      ],
      "id": "fr-доброу-cu-adj-VP3saSn8"
    },
    {
      "form_of": [
        {
          "word": "добро"
        }
      ],
      "glosses": [
        "Génitif-locatif duel de добръ, добра et добро."
      ],
      "id": "fr-доброу-cu-adj-BHeuO8xl"
    }
  ],
  "tags": [
    "form-of"
  ],
  "word": "доброу"
}

{
  "categories": [
    "Formes d’adjectifs en vieux slave",
    "vieux slave"
  ],
  "lang": "Vieux slave",
  "lang_code": "cu",
  "pos": "adj",
  "pos_title": "Forme d’adjectif",
  "senses": [
    {
      "form_of": [
        {
          "word": "добръ"
        }
      ],
      "glosses": [
        "Datif singulier de добръ."
      ]
    },
    {
      "form_of": [
        {
          "word": "добро"
        }
      ],
      "glosses": [
        "Génitif-locatif duel de добръ, добра et добро."
      ]
    }
  ],
  "tags": [
    "form-of"
  ],
  "word": "доброу"
}